Injury is the leading cause of mortality among Americans under 45 years of age, and traumatic brain injury (TBI) is responsible for the majority of these deaths. The absence of clinically useful diagnostics has severely impeded effective management and treatment of TBI. Currently available diagnostics are either expensive and/or unreliable and, there are no simple, rapid, non-invasive tests to diagnose and assess the magnitude of TBI, as well as to predict outcome. Immunoassay technology, such as the enzyme-linked immunosorbent assay (ELISA) method can be employed to develop this much-needed TBI diagnostic test. Such a test would also help predict the efficacy of potential therapies to treat injury as well as provide information on precise biochemical and molecular mechanisms contributing to injury, recovery of function and/or therapeutic effectiveness. We have developed a specific and sensitive biomarker for TBI that preliminary experiments show to be correlated with severity of injury and sensitive to therapeutic intervention. Moreover, this biomarker provides direct assessments of pathobiological mechanisms involved in destruction of the cytoskeletal protein, alpha II-spectrin (spectrin breakdown product 150; SBDP150). THE OVERALL OBJECTIVE OF THIS PROPOSAL IS TO DEVELOP A NOVEL DIAGNOSTIC PROTOTYPE ELISA KIT FOR THE QUANTITATIVE DETERMINATION OF THE SBDP150 BIOMARKER IN CEREBROSPINAL FLUID (CSF). Specific Aim 1: Configuration of sandwich ELISA for the quantitative and specific detection of a calpain mediated SBDP150. Deliverable from Specific Aim 1: Configuration of a diagnostic ELISA kit for the quantitative detection of SBDP150. (Months 0-4) Specific Aim 2: Preliminary validation of the utility of the SBDP150 sandwich ELISA in a rat model of TBI. Deliverable from Specific Aim 2: Prototype diagnostic ELISA capable of measuring SBDP150 levels in CSF and sensitive to different injury magnitudes. (Months 5-6)